@Devanshu1214 

Would you be able to provide a screenshot of the warning message you are seeing, ideally from a windows device?

Also any details you have of the router you are connected too and your ISP?

What happens when you try to access the internet during the prompt warning?   are you able to continue or prompted to accept something?   again any screenshots would help

My gut feeling at this time is its something be passed by your Router, I know BT in teh UK have a setting that causes this.  Its an internet protection wizard type thing you have to go through and best to disable it